Energy Efficient Transmissions in MIMO Cognitive Radio Networks
In this paper, the authors consider energy efficient transmissions for MIMO cognitive radio networks in which the secondary users coexist with the primary users. They want to optimize the proper time allocations and the beam forming vectors for the secondary users, in order to minimize the total energy consumption of the secondary users while satisfying secondary users' rate requirements and the primary receivers' received interference constraints. The joint time scheduling and beamforming optimization is non-convex and is often highly complex to solve. Fortunately, they show that the optimal time allocation and the optimal beam forming vectors can be found very efficiently in polynomial-time through a proper decomposition.